>> first of all, michael leiter, that is one of the terrific under reported stories thus far. the trauma teams at these world class hospitals all of them, five or six of them, within four or five-minute ambulance ride of the blast site. that is a hugely underreported story and god bless them for everything they did. the question that i have for you is the progress of the investigation. i was speaking to several people yesterday involved in the investigation. maybe you can flush this out a bit. it seems that they are quite confident in the direction that they are headed and what they have received so far. if you want to liken it to a murder scene, is it not accurate to say that they have kind of a partial fingerprint here in the sense that they have a piece of a pressure cooker, they have remnants of a bag, they have the outlines, the ingredients of the bomb, so i would think that that would be a huge step down this progress road, would it not be? >> i think it is. the analogy to a fingerprint is good although it's a little imperfect and because a fingerprint is distinct to one